This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-91964 filed on Mar. 28, 2001; the entire contents of this prior application being incorporated herein by reference.
1. Field of Invention
The present invention relates to a paper bag, and more particularly to a paper bag that is improved so as to be easily processed during recycling when the paper bag is discarded after the content therein has been removed.
2. Description of the Related Art
Conventionally, a paper bag made primarily of craft paper and to be filled with, for example, animal feed, cement, grain, fertilizer or resin pellets (hereinafter termed, xe2x80x9ccontentxe2x80x9d) for transport the content is sealed after filling with content, by folding back the opening edge and using a resin hot-melt adhesive to secure the folded back opening edge to the facing wall surface.
Specifically, in a paper bag with gussets on both sides that is made of craft paper and cut in steps, a resin hot-melt adhesive has been applied and dried on at least the stepped surface at an opening for filling with the content, so that, when this paper bag is used, a sealing device known as a xe2x80x9ctop sealerxe2x80x9d is used to seal this opening after the content is filled through this opening.
The top sealer blows hot air against the hot-melt adhesive, which had been coated and then cooled onto the stepped surface in advance, thereby not only reactivating the hot-melt adhesive, but also folding the step-cut edge part at a specific location, fastening it to opposite wall surface using the reactivated hot-melt adhesive.
It should be noted that this type of hot-melt adhesive is dry and solid until it is used for sealing, preventing inadvertent adhesion. And merely by blowing the hot air against it, the hot-melt adhesive is easily and immediately reactivated to form an adhesive that has an extremely high adhesive strength and does not peel easily. Therefore, this type of hot-melt adhesive material is used broadly in this type of paper bags as an extremely convenient adhesive.
However, from the perspective of resource conservation, there have been increasing demands in recent years to recycle products, and this type of paper bag is not an exception. In order to prevent contamination, this type of paper bag is mostly not reused after it has been filled with content such as described above and used for transport, and thus this type of paper bag is normally subjected to incineration processes.
However, recent requirements for recycling resources have included plans to use recycled paper for these types of paper bags as well. However, the hot-melt adhesive that is used for sealing the content fill openings of these paper bags, has become an impediment to recycling. This is because the paper bags are to be dissolved in water when they are recycled after use.
On the other hand, the hot-melt adhesive used for sealing the content fill opening is kept to be adhered to the paper bag even after use of the bags. Generally, polymers, such as thermoplastic polymers, are used as the hot-melt adhesive, and when in use, the hot-melt adhesive is melted through the application of heat. Since the thermoplastic polymers used as the hot-melt adhesive do not dissolve in water, such hot-melt adhesive may get caught on the filters in the recycling process, which has been a problem in that it interferes with the recycling processes.
The above would be resolved by using a water-soluble adhesive such as polyvinyl alcohol as the hot-melt adhesive for sealing the content fill opening. However, when adhering a water-soluble adhesive, the evaporation of the water in the adhesive takes a long time. Therefore, such water-soluble adhesives are ill-suited as adhesive for use in sealing the paper bags after the content is fill therein.
Additionally, this type of water-soluble adhesive is vulnerable to water even after the adhesion has been effected, that is, after being hardened unless the adhesion is made completely secure over time. Thus, there is the danger of a serious problem in that the sealed part may be peeled off, causing the content to leak. This is likely to occur when the paper bag is stored for an extended period of time in a high-humidity location after it has been filled with content.
Although it is necessary to remove the hot-melt adhesive from the paper bag when recycling the paper bag after use, it is difficult to remove only the hot-melt adhesive from the paper bag. Therefore, workers have used knives, for example, to cut off the portion of the paper bag to which the hot-melt adhesive has been adhered, or have used cutting machines to cut off certain parts of the bag.
In recycling process for this type of paper bag, the part to which the hot-melt adhesive is adhered has been cut from the paper bag in this way to separate from a part to which there is no hot-melt adhesive adhered. And the part with no hot-melt adhesive has been dissolved in water. However, the considerable labor was involved in cutting off the part of the paper bag to which the hot-melt adhesive is adhered after use in order to separate the two. This has lead to problems with excessive costs in preparing this type of paper bag for the recycling process.
An object of the present invention is to provide a paper bag that is the solution to the conventional problems, a paper bag wherein it is possible to remove with ease, in the recycling process, the portion of the bag to which the hot-melt adhesive is adhered, even when using an extremely convenient non-water-soluble hot-melt adhesive, such as thermoplastic polymers, in sealing the content fill opening.
The paper bag of the present invention comprises a paper bag body, one end of which is closed with a closure flap that is equipped in a gusseted tubular trunk part such that a portion of the closure flap protrudes from an edge or edges of one end and/or another end of the trunk part, said closure flap closing said one end to form a bottom part of the bag, or closing said another end being used as an opening through which the paper bag body is filled with a content after the content is filled through the opening; a non-water-soluble hot-melt adhesive that is coated on a surface of said portion of said closure flap that protrudes from the edge of said paper bag body; and an underlining paper piece that is adhered in advance with a water-soluble adhesive to a part of one wall surface of said paper bag body that overlaps the closure flap when said closure flap is folded along with said end of the paper bag body and is adhered to said wall surface by reactivating said non-water-soluble hot-melt adhesive, wherein, said underlining paper piece can be peeled from said wall surface of said paper bag body or can be peeled away between layers of said underlining paper piece.
Additionally, the paper bag of the present invention comprises a paper bag body, which is closed at a bottom part and is opened at an opening; a closure flap equipped in said paper bag body so that a portion of the closure flap protrudes from an edge of said opening of said paper bag body through which content is removed from said paper bag body after said paper bag body is filled with the content; a non-water-soluble hot-melt adhesive that is coated on a surface of said portion of said closure flap that protrudes from the edge of the opening of said paper bag body; and an underlining paper piece that is adhered in advance with a water-soluble adhesive to a part of one wall surface of said paper bag body that overlaps the closure flap when said closure flap is folded along with said edge of the opening of the paper bag body end and is adhered to said wall surface by reactivating said non-water-soluble hot-melt adhesive, wherein, said underlining paper piece can be peeled from said wall surface of said paper bag body or can be peeled away between layers of said underlining paper piece.
Further, in the paper bag of the present invention, when the closure flap is torn in the cross-wise direction when opening the paper bag, the remaining pieces adhered with the hot-melt adhesive are adhered to the paper bag body with a water-soluble adhesive. Furthermore, in the paper bag of the present invention, the underlining paper piece adhered to the wall surface of the paper bag trunk unit is provided with a handle part across the entire end positioned at the edge of the wall surface side of the paper bag body, or provided with a grip part at a corner thereof. Still further, the closure flap is provided with an opening tape.
By doing the above, it becomes extremely easy to perform the operation when peeling the underlining paper piece from the wall surface of the paper bag body. The paper bag provided with the characteristics described above can also be applied to paper bags that are provided with folded parts (gussets) with V-shaped cross sections on both sides of the paper bag body. Additionally, in the paper bag of the present invention, it is preferable for the inside of the paper bag body to be equipped with an inner bag made from a material other than paper.
This inner bag can be made from, for example, a resin film, providing moisture resistance. The inner bag can also be fabricated from thin sheets of metallic material, providing this type of paper bag with anti-moisture properties and a gas barrier.